The present invention relates to selected liquid 2-aryl-2H-benzotriazoles which are useful in protecting light-sensitive organic materials from deterioration and to stabilized compositions containing said benzotriazoles.
The UV-absorber of the o-hydroxyphenyl-2H-benzotriazole class have long been known as effective light stabilizers for organic materials and have enjoyed considerable commercial success.
The description, preparation and uses of these valuable 2-aryl-2H-benzotriazoles are further taught in U.S. Pat. Nos. 3,004,896; 3,055,896; 3,072,585; 3,074,910; 3,189,615 and 3,230,194.
However the hitherto known 2-aryl-2H-benzotriazoles of this group have in some circumstances exhibited limited compatibility in certain substrates, and excessive tendency to exude, sublime and/or volatilize during processing of stabilized compositions into sheets, films, fibers or other pellicles when processing must be done at elevated temperatures. Likewise such benzotriazoles may also suffer undue loss by volatilization or sublimation from fabricated structures, particularly thin films or coatings, especially when subjected to elevated temperatures during use.
Attempts have been made to increase compatibility and to reduce volatilization loss by modifying the structure of the benzotriazoles.
In U.S. Pat. No. 3,230,194, a higher alkyl group was substituted for methyl and the latter compound 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole exhibited superior compatibility and performance in polyethylene compared to the former.
In U.S. Pat. Nos 4,283,327, 4,278,590 and 4,383,863 there is described 2-(2-hydroxy-3,5-di-tert-octylphenyl)-2H-benzotriazole which exhibits an excellent combination of compatibility with and/or solubility in numerous polymeric substrates along with superior resistance to loss from stabilized compositions during high temperature processing or in end-use applications where coatings or films of the stabilized compositions are exposed even to ambient weathering and light exposures, and in photographic applications. However, 2-(2-hydroxy-3,5-di-tert-octylphenyl)-2H-benzotriazole is still a solid (melting point 105.degree.-106.degree. C.) which requires in many end-use applications the concomitant use of a solvent or dispersing diluent to allow for it to be used in practice. Such solvents or diluents are undesired for reasons of cost and environmental and other considerations.
U.S. Pat. Nos. 3,983,132, 4,096,242 and 4,129,521 describe liquid mixtures of 2-(2-hydroxy-5-nonylphenyl)-2H-benzotriazoles or of 2-(2-hydroxy-5-dodecylphenyl)-2H-benzotriazoles and stabilized compositions using said mixtures where the nonyl or dodecyl groups each represent an isomeric mixture of secondary and tertiary nonyl or dodecyl groups attached to the para position relevant to the hydroxy group on the 2-phenyl moiety in the 2H-benzotriazole. The isomeric nonyl or dodecyl groups are introduced into the phenol before it is coupled with the 2-nitrophenyldiazonium salt in a classic 2H-benzotriazole synthesis.
The instant liquid benzotriazoles differ from the benzotriazoles of these three patents by the method by which they are prepared, by the location of the branched alkyl group ortho to the hydroxy group and by in part the nature of the branched alkyl group itself when prepared from a straight chain alkene.
The liquid mixtures prepared by the method of U.S. Pat. No. 4,129,521 have no substitution in the ortho position relevant to the hydroxy group thus making said compounds prone to interaction with metal ions during resin curing and in other end-use applications in polymer substrates and which may lead to deleterious effects on color, light stability and ancillary properties. The instant mixtures are substituted in the ortho position relevant to the hydroxyl group and do not have this problem.
Certain hydrophobic non-diffusing hydroxyphenylbenzotriazoles are disclosed as very useful as ultraviolet light absorbers in photographic gelatin layers (U.S. Pat. No. 3,253,921). The instant benzotriazoles with their liquid or non-crystalline nature, their desirable absorption characteristics in the ultraviolet range and their photographic inertness are particularly useful in photographic compositions, especially in protecting color dye images against the harmful effects of ultraviolet light.
U.S. Pat. No. 3,253,921 discloses benzotriazoles broadly, but does not exemplify the instant benzotriazoles which are particularly effective in stabilizing photographic compositions against the harmful effects of ultraviolet radiation.
Further background in the area of stabilization of photographic dye images is provided by U.S. Pat. No. 4,042,394 which describes the various components in photographic compositions and the requirements for stabilizing photographic dye images.
U.S. Pat. Nos 4,383,863 and 4,447,511 describe the use of 2-(2-hydroxy-3,5-di-tert-octylphenyl)-2H-benzotriazole in photographic elements and compositions. While this discrete benzotriazole exhibits enhanced solubility in the various solvents and diluents used in photographic elements, such solvents and diluents are still required since said benzotriazole is still a crystalline solid.
The instant benzotriazole mixtures are liquid or non-crystalline leading to the need for less or no solvent or diluent, thinner photographic layers and all the concomitant economic benefits flowing therefrom.